1. Technical Field
The present invention relates in general to composite tooling and, in particular, to an improved system, method, and apparatus for improved, low cost composite tool fabrication of composite parts.
2. Description of the Related Art
Composite carbon fiber tooling for fabrication and cure of composite parts has traditionally offered several advantages, including significantly lower weight, which facilitates ease of handling. If designed and fabricated properly, composite tooling can also provide precise match-up of a tool's coefficient of thermal expansion (CTE) to that of the part. In addition, composite tooling has a low thermal mass, such that heat up and cool down becomes much more efficient than that of metallic (e.g., INVAR) tooling. Moreover, composite tooling provides close replication of original master model dimensions and contours, and reduced acquisition lead time as compared to metallic tooling.
However, typical composite tooling also has deficiencies which, in many cases, preclude its use for production. These deficiencies include high material and labor costs, such as those for prepregs, protracted lay-up time, long autoclave compaction and cure cycles. Composite tooling also exhibits poor surface durability and/or vacuum integrity since polymeric surfaces do not last long in a production environment. In addition, composite tooling typically uses archaic and expensive methods to attach an “egg crate” type structural support to the tool substrates. It also has inherent weakness in the substrate-to-egg crate attachment schemes (e.g., the tool dimensional stability erodes over time). Moreover, an intermediate tool fabrication step is usually required since machined master models cannot hold tolerances when subjected to elevated cure temperatures. This adds significant cost to the final product, and increases the risk of dimensional tolerance build-up. Furthermore, there is degradation of tool laminates due to thermal cycling since epoxy tools cannot handle much more than 100 cycles.
Of the various problems previously stated, only the last one has been addressed by the composite tooling industry, primarily through the use of bismaleimide (BMI) prepregs. As such, only the life cycle cost of composite tools has been reduced. The move by some in the industry toward prepreg BMI tools has done nothing to address the exorbitant acquisition costs of prepreg tooling, or their susceptibility to both surface and substructure damage. The acquisition costs are so high and the long term durability of typical composite tools is so low, that it can be more cost effective to use metallic (e.g., INVAR) tooling. This can be true even when factoring the higher cost of handling heavy INVAR tools, their inefficient heat up and cool down rates, and their dimensional inaccuracies and/or instability. Thus, an improved solution for fabricating composite tooling would be desirable.